Typically, a conventional arm member for use as an automobile suspension arm is comprised of a machined aluminum casting, iron casting or formed steel structure and a pair of elastomeric bushings pressed in each end of the member. In the case of a tubular formed steel structure, various fusion welding (MIG welding, TIG welding or laser welding), or friction agitation welding, have been developed to connect the coupling members to the tubular member at a joined portion. Known casting methods include those disclosed in U.S. Pat. Nos. 5,332,026, 5,429,175, 5,660,223, 6,467,528, and 6,745,819, the entire contents being incorporated herein by reference.
However, a conventional suspension arm member, for example, in which the main body and the coupling member are joined by using a welding method, such as fusion welding (MIG welding, TIG welding, laser welding, or the like) or a solid-phase welding method (friction agitation welding), may cause cracks at or proximate to the joined portion when a tensile load is imparted thereto resulting in separation of the joined members and reduced functionality. Further, to achieve a reduction in mass of the connecting member, the connecting member may be tubular in shape. Conventionally, the connecting member and coupling members are of similar chemical composition or metallurgically compatible to permit use of a fusion welding process used to connect the members to achieve the strength and corrosion resistance requirements of the product. Thus, there is a need to provide a component for an automobile suspension, structure, body or power train application that is light in weight and void of potential quality issues related to strength, cracks and corrosion.
Conventional aluminium high pressure die casting utilizes a hydraulic cylinder to advance a shot tip, displacing molten aluminium from the shot sleeve into the die cavity, overcoming the resistance to flow through the restricted gate area. When the die cavity is filled with molten aluminium, the pressure applied to the hydraulic shot cylinder is transferred to the molten aluminium based upon the ratio of the shot cylinder and shot tip cross-sectional area. If the die cavity containing one end of a submerged member fills and becomes pressurized before the die cavity or region of the die containing the opposing end of the submerged member, a resultant force is imposed on the end of the submerged member. To avoid movement of the submerged member, a mechanism must be employed, such as a clamp or a friction or form fitting die, to resist the force. As the cross-sectional area of the member increases, the forces become very high and difficult to manage with such mechanisms. Subsequent to filling of the die cavity, the pressure applied to the hydraulic cylinder advancing the shot tip is typically increased (i.e., intensified) by, for example, a factor of two times to reduce the volume of entrapped air and increase the rate of heat transfer. Also, once the in-gates have frozen-off through solidifying, which usually occurs prior to the solidifying of the entire die cavity, even the increased pressure fails to reach the material within the cavities being molded.
U.S. Pat. No. 3,664,410 to Groteke and U.S. Pat. No. 4,779,666 to Ruhlandt et al., disclose each a die casting process and apparatus.